1. Field of the Invention
The present invention relates to a picture encoding apparatus for encoding a digital picture signal in such a manner that the data amount thereof is reduced, a picture encoding method thereof, a picture encoding and transmitting method thereof, and a picture record medium thereof. In particular, the present invention relates to a picture encoding apparatus for encoding a digital picture signal and transmitting additional information along with the encoded information, a picture encoding method thereof, a picture encoding and transmitting method thereof, and a picture record medium thereof.
2. Description of Related Art
FIG. 1 is a block diagram showing a structure of a picture encoding apparatus that compresses a digital picture signal. The picture encoding apparatus shown in FIG. 1 is an encoding apparatus corresponding to the ADRC (Adaptive Dynamic Range Coding) method. The encoding apparatus divides the input picture signal into blocks and adaptively encodes pixels of each block corresponding to the dynamic range of the block.
The ADRC method has been proposed by the applicant of the present patent application as U.S. Pat. No. 4,703,352 issued on Oct. 27, 1987 (corresponding to Japanese Patent Laid-Open Publication No. 61-14498 laid open on Jul. 2, 1986). Next, with reference to FIG. 1, the ADRC method will be described in brief. An input picture signal is supplied form an input terminal 120 to a block dividing portion 121. The block dividing portion 121 divides the input picture signal into blocks each of which is composed of for example 9 pixels (3 pixels.times.3 lines) (hereinafter referred to as a block of (3.times.3) pixels). The output signal for each block is supplied from the block dividing portion 121 to a maximum value detecting portion 122 and a minimum value detecting portion 123.
The maximum value detecting portion 122 detects the maximum value MAX of the pixel values of the block. The minimum value detecting portion 123 detects the minimum value MIN of the pixel values of the block. The maximum value MAX is supplied from the maximum value detecting portion 122 to a subtracting portion 124. On the other hand, the minimum value MIN is supplied from the minimum value detecting portion 123 to the subtracting portion 124, a subtracting portion 125, and a framing portion 128.
The subtracting portion 124 subtracts the minimum value MIN from the maximum value MAX and generates a dynamic range DR. The dynamic range DR is supplied to a quantizing step width calculating portion 126 and the framing portion 128. The quantizing step width calculating portion 126 calculates a quantizing step width .DELTA. with the dynamic range DR supplied from the subtracting portion 124 and supplies the calculated quantizing step width .DELTA. to a quantizing portion 127.
The block dividing portion 121 also supplies 9 pixels of the block of (3.times.3) pixels to the subtracting portion 125. The subtracting portion 125 subtracts the minimum value MIN from each of the 9 pixel values. Thus, each pixel value is normalized. Each normalized pixel value is supplied to the quantizing portion 127. The quantizing portion 127 quantizes the normalized pixel values with the quantizing step width .DELTA. and supplies quantized values x to the framing portion 128.
The framing portion 128 frames the dynamic range DR and the minimum value MIN supplied as parameters for each block and the quantized values x of the 9 pixels of the block and obtains an output signal. The output signal is recorded on a record medium such as a disc or transmitted through a transmission line.
However, in the case that the quantized values of the block are decoded with the parameters on the recording side, to minimize a decoded error between original signal values and restored values, it is not assured that quantized values of the block are optimally decoded with parameters of a block that have been initially obtained. Occasionally, the decoded error becomes large and thereby the decoded picture may deteriorate.